1. Field of the Invention
The invention relates to a method for producing shaped articles from reaction-bonded, silicon-infiltrated silicon carbide and/or boron carbide according to the preamble of claim 1 and a shaped article thus produced according to claim 9.
2. Background Art
Known from DE 42 43 864 C2 is a method for the producing of shaped articles from reaction-bonded, silicon-infiltrated silicon carbide in which an appropriate slurry is produced and is cast in a mould to form a green body. The green body is then dried and, after the drying, heated in contact with liquid or gaseous silicon. This casting method is however complex or not applicable when large shaped articles, shaped articles with undercuttings or shaped articles with highly differing wall thicknesses are to be produced. Such shaped articles are therefore put together by elaborately combining several parts. Apart from the effort required, the joints continually cause problems in the processing and durability.
From DE 10 2005 003 197 B4 is known a method in which a slurry is also used for the production of shaped articles from reaction-bonded, silicon-infiltrated silicon carbide is well known. The slurry is made from fine-grain silicon carbide, colloidal carbon, additives and a liquid medium. The slurry together with a fibrous textile material with a carbon residue of at least 50% after pyrolysis is formed in a layered way. In this, the textile material prevents crumbling of the drying and therefore shrinking, slurry. In addition, a uniform reaction-bonded, silicon-infiltrated silicon carbide body can be produced by heating at a later date.
Further, from EP 1 284 251 B1 is known to produce a porous and correspondingly lightweight and structured ceramic material based on silicon carbide in which a framework with a porous structure such as corrugated cardboard or a fabric is impregnated with a slurry made from a resin as carbon source, and a powdered silicon is carbonised to react with the silicon, and then is infiltrated with the liquid silicon in order to close the pores formed by the reaction of the silicon with the carbon, but to maintain the structure of the framework i.e. roughly the structure of the corrugated cardboard or of the fabric. Such fibre-reinforced silicon carbide composites are suitable for applications that require an improved toughness. The silicon carbide composites obtained are however only simple, dense fibre-reinforced shaped articles.